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PubMed1996

Rhodococcus percolatus sp. nov., a bacterium degrading 2,4,6-trichlorophenol.

A bacterial strain that was able to mineralize 2,4,6-trichlorophenol was isolated from a chlorophenol-fed percolator and was identified as a member of the genus Rhodococcus on the basis of chemotaxonomic characteristics and 16S RNA phylogenetic inference data. This organism (strain MBS1T [T = type strain]) exhibited a typical irregular rod-coccus cycle, and the cells had fimbria-like structures on their surfaces. The diagnostic cell wall amino acid was meso-diaminopimelic acid, and the sugars were arabinose and galactose; the mycolic acids contained 46 to 54 carbon atoms. The main menaquinone was MK-8(H2), and MK-9(H2) was a minor component. The cellular phospholipids were phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositolmannoside, phosphatidylglycerol, and diphosphatidylglycerol. Tuberculostearic acid was present. The whole-cell fatty acids were straight-chain acids with 14 to 18 C atoms. The G+C content of the DNA was 67.4 mol%. This organism grew on sucrose, pyruvate, and 2,4,6-trichlorophenol, and it oxidized a large number of carbon compounds, including catechol, 3-hydroxyphenylacetic acid, and phenol. It also exhibited beta-galactosidase, urease, and 2-acetyl-lactate decarboxylase activities. On a phylogenetic tree that was based on 16S ribosomal DNA gene sequences strain MBS1T was found among the rhodococci on an independent branch. On the basis of the chemotaxonomic and phenotypic characteristics of strain MBS1T and its phylogenetic position we suggest that this bacterium should be placed in a new species, Rhodococcus percolatus; the specific epithet was chosen because the organism was isolated by using an enriched percolator. The type strain is strain MBS1.

Base Sequence↗
PubMed1971

Lactate metabolism by Veillonella parvula.

A strain of Veillonella parvula M4, which grows readily in lactate broth without a requirement for carbon dioxide, has been isolated from the oral cavity. Anaerobic, washed cells of this organism fermented sodium lactate to the following products (moles/100 moles of lactate): propionate, 66; acetate, 40; carbon dioxide, 40; and hydrogen, 14. Cells grew readily in tryptone-yeast extract broth with pyruvate, oxaloacetate, malate, and fumarate, but poorly with succinate. The fermentation of pyruvate, oxaloacetate, or lactate plus oxaloacetate by washed cells resulted in the formation of propionate and acetate in ratios significantly lower than those observed with lactate as the sole carbon source. This was primarily due to increased acetate production. Cell-free extracts were unable to degrade lactate but metabolized lactate in the presence of oxaloacetate, indicating the presence of malic-lactic transhydrogenase in this organism. Lactic dehydrogenase activity was not observed. Evidence is presented for oxaloacetate decarboxylase and malic dehydrogenase activities in extracts.

Acetates↗
PubMed1979

Mechanism of acetate synthesis from CO2 by Clostridium acidiurici.

Total synthesis of acetate from CO2 by Clostridium acidiurici during fermentations of hypoxanthine has been shown to involve synthesis of glycine from methylenetetrahydrofolate, CO2, and NH3. The glycine is converted to serine by the addition of methylenetetrahydrofolate, and the resulting serine is converted to pyruvate, which is decarboxylated to form acetate. Since CO2 is converted to methylenetetrahydrofolate, both carbons of the acetate are derived from CO2. The evidence supporting this pathway is based on (i) the demonstration that glycine decarboxylase is present in C. acidiurici, (ii) the fact that glycine is synthesized by crude extracts at a rate which is rapid enough to account for the in vivo synthesis of acetate from CO2, (iii) the fact that methylenetetrahydrofolate is an intermediate in the formation of both carbons of acetate from CO2, and (iv) the fact that the alpha carbon of glycine is the source of the carboxyl group of acetate. Evidence is presented that this synthesis of acetate does not involve carboxylation of a methyl corrinoid enzyme such as occurs in Clostridium thermoaceticum and Clostridium formicoaceticum. Thus, there are two different mechanisms for the total synthesis of acetate from CO2 by clostridia.

Acetates↗
PubMed1992

S-adenosylmethionine decarboxylase as an enzyme target for therapy.

The polyamine biosynthetic pathway has attracted much interest as a therapeutic target. Many studies have shown the potential value of inhibitors of the first enzyme in the biosynthetic pathway, ornithine decarboxylase, which forms putrescine. In order to convert putrescine into the polyamines, spermidine and spermine, the aminopropyl donor, decarboxylated S-adenosylmethionine, is needed. Therefore, S-adenosylmethionine decarboxylase (AdoMetDC, EC 4.1.1.50) is essential for polyamine synthesis. Early studies of the inhibition of this enzyme were carried out with compounds such as methylglyoxal bis(guanylhydrazone) that lack specificity and also lack potency since they are competitive inhibitors whose effects are overcome by a compensatory increase in the amount of the target enzyme. Recently, powerful irreversible inhibitors of AdoMetDC have become available including 5'-([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxyadenosine, an enzyme activated inhibitor and 5'-deoxy-5'-[(3-hydrazinopropyl)methylamino]adenosine which binds to the active site and forms a covalent bond with the pyruvate prosthetic group. This review describes the current state of knowledge of the structure and properties of AdoMetDC, the available inhibitors of this enzyme, their mechanism of action and their effects on polyamines and on the growth of tumors and protozoan parasites. These effects indicate that AdoMetDC inhibitors may be of therapeutic value either alone or in combination with ornithine decarboxylase inhibitors and that further trials of these compounds should be considered.

Adenosylmethionine Decarboxylase↗
PubMed1991

The origin of free brain malonate.

Rat brain contains substantial concentrations of free malonate (192 nmol/g wet weight) but origin and biological importance of the dicarboxylic acid are poorly understood. A dietary source has been excluded. A recently described malonyl-CoA decarboxylase deficiency is associated with malonic aciduria and clinical manifestations, including mental retardation. In an effort to study the metabolic origin of free malonate, several labeled acetyl-CoA precursors were administered by intracerebral injection. [2-14C]pyruvate or [1,5-14C]citrate produced radioactive glutamate but failed to label malonate. In contrast, [1-14C]acetate, [2-14C]acetate, and [1-14C]butyrate were converted to labeled glutamate and malonate after the same route of administration. The intracerebral injection of [1-14C]-beta-alanine as a precursor of malonic semialdehyde and possibly free malonate did not give rise to radioactivity in the dicarboxylate. The labeling pattern of malonic acid is compatible with the reaction sequence: acetyl-CoA----malonyl-CoA----malonate. The final step is thought to occur by transfer of the CoA-group from malonyl-CoA to succinate and/or acetoacetate. Labeling of malonate from acetate is most effective at the age of 7 days when the net concentration of the dicarboxylic acid in rat brain is still very low. At this age, butyrate was a better precursor of malonate than acetate. It is proposed that fatty acid oxidation provides the acetyl-CoA which functions as the precursor of free brain malonate. Compartmentation of malonate biosynthesis is likely because the acetyl-CoA precursors citrate and pyruvate are ineffective.

Acetates↗
PubMed1994

Involvement of L-tryptophan aminotransferase in indole-3-acetic acid biosynthesis in Enterobacter cloacae.

L-Tryptophan aminotransferase (L-tryptophan:2-oxoglutarate aminotransferase; EC 2.6.1.27) from Enterobacter cloacae was purified 62-fold and characterized to determine its role in indole-3-acetic acid biosynthesis. The enzyme reversibly catalyzed the transamination of L-tryptophan with 2-oxoglutarate as the amino acceptor to yield indole-3-pyruvic acid and L-glutamate, and the Km values for L-tryptophan and indole-3-pyruvic acid were 3.3 mM and 24 microM, respectively. In the indole-3-acetaldehyde synthesis experiments in vitro, 94% of L-tryptophan was efficiently converted to indole-3-acetaldehyde by the purified L-tryptophan aminotransferase plus indolepyruvate decarboxylase. Furthermore, the amounts of L-tryptophan decreased with increases in the indolepyruvate decarboxylase activity, while the amounts of indole-3-acetaldehyde increased with increases in this activity. In genetic experiments, the amounts of L-tryptophan produced by Enterobacter and Pseudomonas strains harboring the gene for indolepyruvate decarboxylase were lower than those produced by these same strains without the gene, while the amounts of indole-3-acetic acid produced by Enterobacter and Pseudomonas strains harboring the gene for indolepyruvate decarboxylase were higher than those produced by these same strains without the gene. These results clearly show that L-tryptophan aminotransferase is involved in the indole-3-acetic acid biosynthesis and that indolepyruvate decarboxylase is the rate-limiting step in this pathway.

Carboxy-Lyases↗
PubMed1990

Site-directed alteration of the active-site residues of histidine decarboxylase from Clostridium perfringens.

To clarify the mechanism of biogenesis and catalysis by the pyruvoyl-dependent histidine decarboxylase (HisDCase) from Clostridium perfringens, 12 mutant genes encoding amino acid substitutions at the active site of this enzyme were constructed and expressed in Escherichia coli. The resulting mutant proteins were purified to homogeneity, characterized, and subjected to kinetic analysis. The results (a) exclude all polar amino acid residues in the active site except Glu-214 as donor of the proton that replaces the carboxyl group of histidine during decarboxylation and, since E214I and E214H are nearly inactive, indicate that Glu-214 is the essential proton donor; (b) demonstrate the importance to substrate binding of hydrophobic interactions between Phe-98, Ile-74, and the imidazole ring of histidine, and of hydrogen bonding between Asp-78 and N2 of the substrate; and (c) demonstrate a significant unidentified role for Glu-81 in the maintenance of the active-site structure. The proposed roles of these amino acid residues are consistent with those assigned on the basis of crystallographic evidence to the corresponding residues at the active site of the related HisDCase from Lactobacillus 30a [Gallagher, T., Snell, E. E., & Hackert, M. L. (1989) J. Biol. Chem. 264, 12737-12743]. Of the residues altered, only Ser-97 was essential for the autocatalytic serinolysis reaction by which this HisDCase, (alpha beta)6, is derived from its inactive, pyruvate-free precursor, proHisDCase, pi 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

[The effect of chronic acidosis on the activity of renal glutamate decarboxylase and GABA-transaminase].

Chronic acidosis evoked by a 7-day application of ammonium chloride in concentration of 2% increased the activity of glutamate decarboxylase (GAD) in renal homogenates of rats to approximately 160%. The enzyme activators, chlorides and adenosine triphosphate influenced in varying measures the GAD activity in renal homogenates of both controlled and acidotic animals. Whilst ATP was gradually loosing the activating effect, chlorides preserved it. The renal GAD is firmly bound on insoluble structures. The increase in GAD activity due to acidosis was accompanied by increasing permanence of this bind. After the substitution of ammonium chloride by drinking water, the return of the increased GAD activity to previous normal values lasted 7 days, whilst apparent normalization of the weight of experimental animals reoccurred on the first day. Subfractionation of the crude renal mitochondrial fraction by use of enzyme markers localized GAD in mitochondria. In renal homogenates the activities of GABA-transaminases were assessed. GABA-alpha-ketoglutarate transaminase was 5x more active than GABA-pyruvate transaminase. Acidosis resulted in augmentation of both transaminases--the first to 130%, the second to 160%. (Tab. 5, Fig. 3, Ref. 25.)

4-Aminobutyrate Transaminase↗
PubMed2000

Respiratory state and phosphatidylserine import in brain mitochondria in vitro.

The mechanism of phosphatidylserine (PS) movement from donor membranes into rat brain mitochondria was investigated. Mitochondria were incubated with liposomes and subjected to density gradient centrifugation. The energized state was monitored by flow cytometry measuring the fluorescence of membrane-potential-sensitive rhodamine-123 dye. Mitochondria density decreased upon increase of the respiratory rate, as a consequence of their association with liposomes. After interaction of mitochondria with (14)C-PS containing liposomes, (14)C-PS became a substrate of PS decarboxylase, as monitored by the formation of (14)C-phosphatidylethanolamine (PE), indicating translocation of (14)C-PS to the inner membrane. The kinetics of (14)C-PE formation showed a high rate upon addition of ADP, malate and pyruvate (state 3) compared to control (state 1). In state 3, (14)C-PE formation decreased in the presence of NaN(3). Mitochondria-associated membranes (MAM) are the major site of PS synthesis. However, their role in the translocation of PS to mitochondria has not been completely elucidated. A crude mitochondrial fraction (P(2)) containing MAM, synaptosomes and myelin was prelabeled with (14)C-PS and incubated in different respiratory states. At a high respiratory rate, low-density labeled mitochondria, whose band overlaps that of synaptosomes, were obtained by centrifugation. A parallel decrease of both radioactivity and protein in MAM fraction was observed, indicating that the association of MAM and mitochondria had occurred. Synthesis and translocation of (14)C-PS in P(2) membranes were also studied by incubating P(2) with (14)C-serine. In the resting state (14)C-PS accumulated in MAM, indicating that the transfer to mitochondria was a limiting step. In state 3 both the transfer rate of (14)C-PS and its conversion to (14)C-PE increased. Respiratory mitochondrial activity modulated the association of MAM and mitochondria, triggering a mechanism that allowed the transport of PS across the outer mitochondrial membrane.

Adenosine Diphosphate↗
PubMed1992

NADP-malic enzyme from plants.

NADP-malic enzyme functions in plant metabolism as a decarboxylase of malate in the chloroplast or cytosol. It serves as a source of CO2 for photosynthesis in the bundle sheath chloroplasts of C4 plants and in the cytosol of Crassulacean acid metabolism plants, and as a source of NADPH and pyruvate in the cytosol of various tissues. Mg2+ or Mn2+ is required as a cofactor. The enzyme has a high specificity and low Km for NADP+. It exists as a tetramer which may undergo changes in oligomerization and exhibit hysteresis. Its kinetic properties vary depending on the compartmentation and function of the enzyme. The chloroplast form in C4 plants has a high pH optimum (pH 8) under high malate, which favours the tetramer, whereas lower pH (pH 7) favours the dimer form. Generally, other forms of the enzyme, which are thought to be cytosolic, have lower pH optima than the chloroplast enzyme. In a number of cases these forms have been shown to have allosteric properties with malate as a substrate. Chemical modifications of the plant enzyme suggest sulphydryl, histidine and arginine residues are required for catalysis. Primary sequence studies on the chloroplastic enzyme from C4 plants show significant similarities to cytosolic NADP-ME in plants and animals, including a sequence motif which is indicative of the NADP+ binding site. The possible origin of the chloroplast form of the enzyme is discussed.

Amino Acid Sequence↗
PubMed1982

Metabolism of dibutylphthalate and phthalate by Micrococcus sp. strain 12B.

Micrococcus sp. strain 12B was isolated by enriching for growth with dibutylphthalate as the sole carbon and energy source. A pathway for the metabolism of dibutylphthalate and phthalate by micrococcus sp. strain 12B is proposed: dibutylphthalate leads to monobutylphthalate leads to phthalate leads to 3,4-dihydro-3,4-dihydroxyphthalate leads to 3,4-dihydroxyphthalate leads to protocatechuate (3,4-dihdroxybenzoate). Protocatechuate is metabolized both by the meta-cleavage pathway through 4-carboxy-2-hydroxymuconic semialdehyde and 4-carboxy-2-hydroxymuconate to pyruvate and oxaloacetate and by the ortho-cleavage pathway to beta-ketoadipate. Dibutylphthalate- and phthalate-grown cells readily oxidized dibutylphthalate, phthalate, 3,4-dihydroxyphthalate, and protocatechuate. Extracts of cells grown with dibutylphthalate or phthalate contained the 3,4-dihydroxyphthalate decarboxylase and the enzymes of the protocatechuater 4,5-meta-cleavage pathway. Extracts of dibutylphthalate-grown cells also contained the protocatechuate ortho-cleavage pathway enzymes. The dibutylphthalate-hydrolyzing esterase and 3,4-dihydroxyphthalate decarboxylase were constitutively synthesized; phthalate-3,4-dioxygenase (and possibly the "dihydrodiol" dehydrogenase) was inducible by phthalate or a metabolite occurring before protocatechuate in the pathway; two protocatechuate oxygenases and subsequent enzymes were inducible by protocatechuate or a subsequent metabolic product. During growth at 37 degrees C, strain 12B gave clones at high frequency that had lost the ability to grow with phthalate esters. One of these nonrevertible mutants, strain 12B-Cl, lacked all of the enzymes required for the metabolism of dibutylphthalate through the protocatechuate meta-cleavage pathway. Enzymes for the metabolism of protocatechuate by the ortho-cleavage pathway were present in this strain grown with p-hydroxybenzoate or protocatechuate.

Dibutyl Phthalate↗
PubMed1986

Glycine decarboxylase multienzyme complex. Purification and partial characterization from pea leaf mitochondria.

The P, H, and T proteins of the glycine cleavage system have been purified separately from pea leaf mitochondria and demonstrate molecular weights of 98,000, 15,500, and 45,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight of P protein by gel filtration was 210,000, indicating that this enzyme has a native homodimer conformation. Reconstitution assays containing purified P, H, and T proteins and yeast lipoamide dehydrogenase catalyze the oxidation of glycine and demonstrate a strict dependence on pyridoxal phosphate, tetrahydrofolate, NAD+, and dithiothreitol. The released CO2, methylamine-H protein intermediate, and methylenetetrahydrofolate are produced in stoichiometric amounts from glycine during the cleavage reaction. H protein acts as co-substrate with glycine during the decarboxylation reaction, demonstrating an apparent Km value of 2.2 microM. P and H protein alone jointly catalyze the glycine carboxyl-14 CO2 exchange reaction in the presence of pyridoxal phosphate and dithiothreitol. L protein of the glycine cleavage system was immunopurified using monoclonal antibodies. Antigenic and molecular weight similarities of the L protein with the lipoamide dehydrogenase component of the pyruvate dehydrogenase complex were shown suggesting the possibility of common isomers of lipoamide dehydrogenase for the two enzyme complexes.

Amino Acid Oxidoreductases↗
PubMed1975

Effect of hashish on brain gamma aminobutyric acid system, blood fibrinolytic activity and glucose and some serum enzymes in the rat.

Adult male rats were exposed to Hashish smoke for 15 min. Certain biochemical parameters were determined. This treatment did not change the brain glutamic acid level, whereas it significantly decreased brain gamma aminobutyric acid level. There was a significant increase in the activity of the brain enzyme forming gamma aminobutyric acid, namely glutamate decarboxylase, as well as in that enzyme metabolizing gamma aminobutyric acid, namely aminobutyrate aminotransferase. However, the increase was much more marked in the case of aminobutyrate aminotransferase, a finding that might explain the decrease observed in brain gamma aminobutyric acid upon exposure to Hashish. Blood glucose and fibrinolytic activity were significantly increased. It was concluded that these changes might be due to an adrenaline releasing effect of Hashish smoke inhalation. Serum lactate dehydrogenase and serum glutamate oxalacetate transaminase activities were significantly increased, whereas serum glutamate pyruvate transaminase activity was unaffected. From these data it was suggested that the source of leakage of these enzyme activities into the blood is probably the skeletal muscles rather than the liver.

4-Aminobutyrate Transaminase↗